Transmissions of this type are known from German patent document No. 2,947,658 and U.S. Pat. No. 4,125,037. In both cases a transmission input shaft is permanently connected with the pump impeller of a hydrodynamic unit and may also be coupled via a bridging clutch with the drive shaft of a variable-pitch belt transmission. A direction-reversing transmission is connected to the output shaft of the belt transmission for direction reversal by means of a sliding sleeve, a jaw clutch, and gears or via a second jaw clutch and gears with an intermediate gear to the output shaft or to a differential for forward or backward movement. Such switchover requires a separate isolating clutch between the drive engine (upstream of the turbine) and the drive shaft of the mechanical stepless drive in order to interrupt the drive coming from the motor during reverse operation.
Transmissions of this type are very large and heavy and controlling them is particularly complicated as the large number of components make them heavy, and the manufacture of such transmissions involves high cost.